1. Field of the Invention
This invention relates to an electronic apparatus, and, more particularly, it is concerned with an electronic apparatus of a construction capable of detachably mounting thereon an external memory device which supplies programs or data stored therein to such electronic apparatus.
2. Description of Prior Art
Conventionally, the electronic apparatuses and appliances such as electronic calculators, etc. having the programming functions are so constructed that an external memory device such as a memory card, etc. storing therein predetermined programs or data in advance is mounted on the main body of the electronic apparatus depending on necessity, thereby making it possible to expand the operational functions of the electronic apparatus. Owing to such construction, users of these electronic apparatuses may be liberated from troublesome operations of making complicated programs and data input by manipulation of the keys arranged on the main body of the electronic apparatus hence these apparatuses become highly convenient and useful.
As an expedient for connecting the external memory device with the main body of the electronic apparatus, thereby making it possible to supply the stored programs and data from the external memory device to the electronic apparatus, there has so far been adopted such a construction that a plurality of connection patterns are formed on the external memory device in an exposed condition, and these connection patterns are brought into contact with a plurality of corresponding contacts provided in advance on the main body of the electronic apparatus.
FIGS. 1 to 3 of the accompanying drawing illustrate a construction of a conventional electronic apparatus using the memory card as the external memory device. In the drawing, the main body of the electronic apparatus, as designated by a reference numeral 1, is composed of an upper casing 1a and a lower casing 1b, both of which are joined together by fitting or screw-connection. In the upper casing 1a, there are provided input means such as keyboard 2, etc. and a display device 3 to display the results of input and output operations. A reference numeral 4 represents a memory card, on one surface side of which a contact pattern 5 appears through a window opening 6. On the other hand, a housing section 7 for the memory card 4 is formed in the rear surface side of the lower casing 1b of the electronic apparatus main body 1. On the bottom surface of this housing section 7, there is provided in a slightly projected state a press-contact type connector 8 so as to be electrically connected with the above-mentioned contact pattern 5. A lid 9 is provided at one edge of the housing section 7 in a freely openable and closable manner. A small projection 9a provided on one end of the lid 9 comes into contact with a movable stopper 10 positioned on the main body opposite to the small projection, and becomes engaged with the stopper 10, while displacing the same, whereby the contact pattern 5 of the memory card 4 placed in the housing section 7 and the press-contact type connector 8 can be kept in a mutually press-contacted condition.
The press-contact type connector 8 has its base part 8a fixedly secured on a printed circuit wiring board 12 with solder, and its top end part protruded from a window opening 11 formed at one part of the bottom surface of the housing section 7. On the other hand, the memory card 4 contains therein a printed circuit wiring board 14 having various memory elements 13 provided thereon. A reference numeral 15 in FIG. 3 designates a rotational shaft for the above-mentioned lid 9.
When adopting such construction, however, there inevitably take place such disadvantages that the contact pattern 5 is corroded to be a cause of poor contact with the connector 8 because the contact pattern 5 is constantly exposed outside from the surface of the memory card 4, and that static electricity is directly applied to the contact pattern 5 to destroy the memory elements 13 in the memory card 4 because the contact pattern 5 is readily accessible.
In order therefore to eliminate such disadvantages as mentioned above, there has been proposed an improved external memory device by the same applicant as in the present application, as shown in FIGS. 4 to 8 of the accompanying drawing.
That is to say, the memory card as the external memory device illustrated in FIGS. 4 to 8 contains the printed circuit wiring board 14 in its lower casing 26. On the upper surface side of this printed circuit wiring board 14, there is disposed a spacer 25 having a window opening 25a formed in one part thereof. This window opening 25a corresponds in position to the contact pattern 5 on the printed circuit wiring board 14.
A guide plate 21 having a size about half that of the spacer 25 is placed on the upper surface side of the spacer. Also, a shutter plate 17 is placed on the upper surface side of the spacer 25 in a state of being complementary to the guide plate 21. The shutter plate 17 has a male part 17a which is slidably fitted in and out of a female part 21a of the above-mentioned guide plate 21. From the upper surface of the male part 17a, projects a knob 18. Further, the shutter plate 17 has a window opening 22 corresponding to the window opening 25a of the spacer 25. Over the upper surface side of the shutter plate 17 and the guide plate 21, there is placed a top plate 20. The top plate 20 has an opening 6 formed therein at a position corresponding to the contact pattern 5, adjacent to which a slot 19 to receive therein the above-mentioned knob 18 is formed in the direction normal to the lengthwise direction of the opening 6.
In the memory card of the above-described construction, an earth pattern 23 is formed on the printed circuit wiring board 14. Further, an earth spring 24 is interposed between the top plate 20 and the printed circuit wiring board 14 with its lower end being in contact with the earth pattern 23 and its upper end with the rear surface of the top plate 20. Accordingly, the shutter plate 17 is connected with the earth pattern 23 through the top plate 20 and the earth spring 24, whereby static electricity is constantly relieved to the earth pattern 23.
When the memory card of such improved construction as mentioned above is adopted, the contact pattern 5 can be kept away from direct contact with an external object by closure of the shutter plate 17 as shown in FIG. 7 during non-use of the memory card 4, whereby there is no possibility of the contact pattern being corroded to bring about poor contact with the connector, and of static electricity destroying the memory elements in the card.
However, even the memory card having the above-described adavantages is not free of disadvantages in opening and closing the shutter plate 17 at the time of its mounting and dismounting. Further, since the shutter plate 17 is made of a metal material of good electric conductivity as the measures to be taken against static electricity, if it is forgotten to open the shutter plate 17 at the time of mounting the memory card, the shutter plate comes inevitably into direct contact with a plurality of contacts in the press-contact type connector 8 to cause short-circuiting among those plurality of contacts. Thus, the risk of destroying the circuits and component parts in the electronic apparatus main body 1 exists. Furthermore, when frequency of opening and closing of the shutter plate 17 increases, a space gap between the top plate 20 and the spacer 25 becomes large with the consequence that the shutter plate 17 tends to open with even a slight shock applied to the card 4 when it is not in use, and the connection pattern 5 is exposed to the outside attracting dust particles, etc. onto it. In this state, when the memory card is mounted on the electronic apparatus, no perfect electrical connection can be made.